AT&T Inc. is close to sealing a takeover of DirecTV that could put a value of nearly $50 billion on the satellite-television provider, people familiar with the matter said.

The two sides are discussing a deal that would involve a mix of cash and AT&T stock, these people said. Dallas-based AT&T would likely pay a premium to DirecTV's share price Monday, one of the people said. An agreement could be reached in two weeks if...